Electrical contact plug



April 16, 1946. c. A. WO ODWARD 2,398,634

I ELECTRICAL CQNTACT PLUG- Filed Dec. 10, 1942 Fb'g. l.

'ZemeaEuZ libodzvarcb Patented Apr. 16,1946

ELECTRICAL CONTACT PLUG Clement A. Woodward, Wellesley, Mass., assignor to United-Carr Fastener Corporation, Cambridge, Mass, a corporation of Massachnsetts Application December 10, 1942, Serial No. 468,529

1 Claim.

The present invention relates to improvements in electrical contact plugs, particularly to those of the so-called banana pin type, and aims generally to improve the construction of such plugs as well as the method of making them.

Electrical contact plugs of the banana pin type. as are commonly used in various electrical apparatus, for example in electrical discharge or thermionic tubes, comprise a central stem and a split sheet metal cage attached thereto, which cage has portions bulged outwardly from the stem soas to make resilient contact with the sockets in to which they are inserted. The central stem preferably has a solid core within the cage, and an integral skirt or flange clinched under a portion of the cage, and an outwardly disposed head which is embedded in the molded base of the tube or other article and to which an electrical conductor is connected.

Heretof ore, the central stem has been a screwmachine made part, and is thus a comparatively slowly and expensive made part. Such parts conventionally comprises a head, a cupped or skirted flange at one end thereof and a solid core disposed below the flange. The cage is placed around the core and the lower skirt of the flange is bent inwardly around portions of the cage to hold the cage and core in assembled relation.

My present invention relates to improvements in the construction and method of making the stem, permitting it to be made from a wire blank very rapidly and economically on a cold-heading machine.

- In order better to illustrate the invention, reference is made to the following drawing in which:

Fig. 1 is a view of the end of a piece of wire from which a core is made;

Fig. 2 is a side elevation of the core after it is formed from the wire shown in Fig. 1;

Fig. 3 is a view of the core and the cage prior to assembly with the disk portion of the core shown in section after being cupped;

Fig. 4 is a side elevation of the complete device after assembly with a portion thereof shown in section to illustrate the manner of assembly;

Fig. 5 is a view illustrating aslightly modified form of the core; and

Fig. 6 is a plan view of the metal blank used in making the cage.

According to the invention, the stem of the plug may be efficiently, quickly and economically formed by first cutting a blank III of predetermined length from a piece of wire stock II of a selected uniform diameter or gauge, as shown in Fig. 1. The blank thus formed is of substantially cylindrical wire stock.

The cylindrical blank thus formed is then subjected to a'cold-heading operation-for the purpose of providing, at one end, a cage core I2 and simultaneously form between its ends a substantially flat disc I3 or rim disposed in a plane normal to the axis of the blank. This may be done in r a conventional cold-heading machine and prefersame time an enlarged head portion I4 is provided above the disc which may be embedded in the molded support base for mounting the plug and effecting an electrical connection with a source of current supply.

The finger cage I5 is preferably formed from a cross-shaped blank of sheet metal having a solid center I6 and a plurality of radially extending fingers IT. The center portion I B is preferably cupped so as to conform to the shape of the nose of the core I2 to provide a good electrical contact with substantially the entiresemi-spherical end of the core I2. The fingers I! extend away from the cupped portion in divergent direction and then in a convergent direction to provide outwardly spaced bulges or resilient bowed portions I8 spaced from said core I2. The terminal ends of the fingers I! are flanged outwardly, as at I9, to bear against the underside of the disc I3 and to be secured in place by turning th peripheral edges of the disc I3 inwardly under the finger flanges, as at 20.

By constructing the stem and disc l3 in the manner above described, I am able to make it rapidly on a cold-heading machine, thus matee rially reducing the cost of manufacture as compared to making such a part on a screw-machine. The wafer-like disc I3 is readily deformable so that it may be clenched under the flnger flange I9 in a single operation.

In the modified form of core shown in Fig. 5 the head portion 14* remains the same diameter as the portion l2.

Advantages of the invention reside in the ease and economy in the manufacture of the plug stem which may be effected on rapidly operating coldheading machines as distinguished from the slower screw-machine made Darts. Furthermore. the invention makes possible the manufacture of in: a solid cupped central portion. spaced bowed resilient fingers extending therefrom which are formed with outwardly turned flanges at their free ends for attachment to said stem, said stem comprising a length of wire having an integral waterlike disc intermediate its ends providing said stem with a head portion and a core for receiving said cage, the peripheral portion of said disc bein! bent around the outturned flanges of said cage fingers for securing said cage thereto in secure electrical contact therewith.

CLEMENT A. WOODWARD. 

